The putty-based composite silicone weather stripping extruded rubber strip was made up of Ethylene-Propylene-Diene Monomer polymer rubber (EPDM foam strip) and the external composite layer (putty paste) of high viscosity reactive polymer cement (butyl rubber). The primary reason for use of the composite was to take advantage of the external putty-based material’s properties of viscosity and superplasticity, which can heal mesoscopic cracks and defects on the surface of concrete structures to improve interface waterproof ability. Cross section dimensions and picture of the rubber strip are shown in Fig. 1.
Figure 2 displays the lateral confinement loading test device, which is composed of two parts: convex shape of the upper part and concave shape of the lower part. The inner and outer diameter of the annular groove was 170 mm and 220 mm, respectively. The upper part has protrusion that squeezes the strip, and the annular groove is set at the lower part of the device with an annular rubber strip installed in it (see Fig. 2c). The length of the EPDM foam rubber in the elastic state has 640 mm, and the compression area is 15,315 mm2. Quasi-stress control was selected for the tests.
Experimental results of the putty-based composite strip under lateral confinement for compressive stress and displacement are provided in Fig. 7. At the early stage of loading, the compressive stress of the composite strip gradually increased with the displacement. It was observed that the displacement dramatically increased and at the later stage of the loading when the load reached at 112.36 kN primarily maintained at 11 mm. At end of the test, the rubber strip was not crushed and the internal EPDM foam rubber after unloading almost recovered to its original shape. The maximum displacement of the putty-based composite rubber strip under lateral confinement was approximately 11 mm, which was brought on by the squeezing of the inner hole of the composite strip raising the internal pore of the EPDM rubber. The instantaneous elastic recovery during the unloading process was 85% of total deformation. The residual deformation of the composite rubber strip was gradually recovered to its original state with time. Eventually, the rubber strip was not damaged. The deformation recovery of the inner elastic material to its original shape can partly drive unrecoverable external putty material.
In the loading process, the two end faces of the rubber sealing strip weatherstrip for window were partially extruded upon loading, since they were not restrained at the end face (see Fig. 8). When maximum deformation was reached, the upper and lower parts of the concrete were in contact with each other.
There was an inflection point in the curves of the rubber strip in the two different grooves, as presented in Fig. 10. Before the point, the internal pore and middle hole of the sealing strip were not tightly compressed signifying that the compression strain increased gradually with compressive stress. Moreover, the relationship between compressive stress and compression strain for the two different sizes of groove were almost the same before the inflection point. At the inflection point, the central hole of sealing strip and the pore of foam rubber were completely compressed. The whole strip was so dense that the compressive force increased sharply with the compression strain. The compressive stresses of the sealing strip in the two different grooves at the inflection points were almost the same and their corresponding compression strain differed by roughly 20%.
In the early stage of compression, the compression moduli of the Waterproof Rubber Seal Strip Gasket were almost the same under the two groove constraints. In the later stage of loading, the compression stress of 6 mm depth of groove was greater than that of 4 mm depth under the same compression strain, and the compressive strain of the 4 mm depth of groove was greater than that of the 6 mm depth of groove under the same stress. This was mainly attributed to the difference in the constraint degree of the groove to the strip at the later stage of loading. In the final stage, the two compression interfaces of the 6 mm depth specimens were close in contact with each other. The remaining space at the joint was rather small, and there was no compression space. However, there was still a large space between the two interfaces of the 4 mm deep specimens. This was mainly due to the sum of the strip deformation and groove depth limit. The bilinear outsourced line was taken as an approximate stress-deformation relation model as shown in Eq
The tests started with two culverts gradually assembled in place. After initial post-tensioning, dial gauges were installed inside the culverts to measure joint space variations in the process of post-tensioning. Simultaneously, the strains on the post-tensioning steel bars were recorded. The water injection pump and water pressure gauges at the lower part of the water injection hole of the box culvert were installed. After the steel bars were set in the duct, the conductor was run through the perforated sheet. The sheet was tightly attached to the concrete surface and bolts fastened. Table 2 provides experimental results of the post-tensioning process. The upper and lower prestressed steel bars were tensioned at the same time, otherwise the friction resulted in the vertical location due to the friction at the bottom so that the two tendons were employed. Upon completion of a post-tensioning cycle, the gap change and steel strain were measured. The bolts were then fastened. The maximum tension force was 180 kN. During the post-tensioning process, strain of steel bars varied linearly, indicating that the post-tensioned steel bars were in the elastic state with strain close to the theoretical value.